The present invention relates to a machine for punching panels and in particular printed circuit panels.
More and more items of equipment are making use of printed circuits that are becoming ever more complex. To solve this problem, it is common place to use multilayer printed circuits. Such multilayer circuits consist in making some number of individual printed circuit plates or panels which are then fixed together and electrical connections are also made between the various layers so as to obtain a complete multilayer printed circuit.
When making the complete circuit, it is naturally necessary to stack the individual printed circuits with great precision in order to succeed in making the final circuit, so it is essential to provide position-marker means in each of the individual printed circuits. This marking is usually performed by means of holes formed through the insulating backing of the printed circuit at locations that are well defined relative to the panel and/or the printed circuit made on the panel.
In addition, it is well known that for reasons of economy, the various steps involved in the manufacture of a printed circuit need to be performed using machines that operate automatically.
European patent application 0 819 504 describes a punching machine which can be fed automatically, which enables the printed circuit plate to be positioned relative to the structure of the machine, and which finally makes it possible to put the various punches of the machine into place so as to make the holes in the desired locations. Nevertheless, in that machine, the final positioning of the holes by punching is obtained with high precision only by means of an initial stage during which the printed circuit panel is positioned relative to the structure of the machine using a table that can be moved in X and Y directions and in rotation. Once the printed circuit panel has been positioned with precision relative to the structure, it is then held stationary by mechanical means. Also, in that machine, the purpose of moving the punches is merely to adapt the machine to printed circuit panels of different dimensions and to the different positions for the reference holes that are to be made in the panels.
In certain types of manufacture, it is found that positioning the printed circuit panel relative to the machine can take up a non-negligible length of time, in particular because of the large dimensions of the panel to be positioned. Further, while the punching operation is being performed, the panel must be held with very great precision while simultaneously avoiding any risk of bending the panel since that would spoil the precision with which the hole is positioned. Unfortunately, it is naturally necessary to have access to both faces of the panel so as to be able to place on opposite sides thereof firstly the punch proper and secondly the die which is associated with the punch.
In addition, positioning holes are often of a shape which is not circular, but which can be oblong so as to provide a better position reference. It is therefore necessary for the machine to be capable not only of making holes in the desired locations, but also for it to be capable of making holes that are non-circular and for these holes to be correctly oriented relative to the panel.
Furthermore, in order to enable such machines to be automated, it is necessary for them to be fed using automatic transfer means.
Finally, the positioning holes must be capable of being made at any point of a panel, and in particular in the center of each side of the panel. This ability must not give rise to the punch block being capable of displacement through an amplitude that is excessive.
The resulting cantilevered-out configuration would run the risk of being prejudicial to the precision with which the punch is finally positioned.
An object of the present invention is to provide a machine for punching a panel, and in particular a printed circuit panel, which mitigates the drawbacks of prior art machines while enabling the operating throughput of the machine to be increased, in particular by simplifying the final positioning operations performed between the panel and the punch tools.
To achieve this object, the invention provides a machine for punching a panel on which the position of each hole to be made is identified by a mark, at least some of the holes being capable of having an outline that is not circular, the machine comprising:
a structure for receiving said panel, said structure presenting X and Y directions;
transfer means for bringing a panel onto said structure in the X direction;
means for holding said panel relative to the structure;
at least four punch blocks, each block being secured to a support, each punch block comprising at least one punch carrier tool and at least one die carrier assembly, the support for two of said blocks being in the form of a gantry to enable said panels to travel in the X direction between said punch carrier tool and said matrix carrier assembly of said two punch blocks;
displacement means for separately moving each punch block relative to the structure in the X and Y directions and in rotation;
optical comparator means for comparing the position of each punch block with the corresponding mark and for generating X and Y and rotation position error information relating to each punch block; and
control means for separately controlling the displacement means in response to the position error information.
It will be understood that in the invention the panel is fixed relative to the structure after it has been prepositioned, and that it is the punch blocks which are positioned with precision in the X and Y directions and in rotation in order to make holes at the intended locations on the panel and to make holes with the desired orientations. It can thus be seen that since the panel is fixed relative to the structure, it is possible to provide means for preventing the panel from moving relative to the structure which are more effective and simpler since these means for holding the panel stationary are themselves functionally fixed relative to the structure.
In addition, the fact that the supports for the punch blocks of at least two of the punch blocks are in the form of a gantry means that the panels can pass between the punch and the die when feeding a panel to the machine and when removing a panel therefrom after the holes have been made.
It will also be understood that, while the machine is being fed with panels, the punch blocks can be prepositioned before final positioning by prior detection of marks that represent the positions of the holes and that are made on the panels.
Preferably, the optical comparator means comprise a camera secured to each punch block.
In this preferred embodiment, the fact that the camera is secured to the punch block and that the block is itself prepositioned means that the camera need have only a small field of view, thereby giving an image that is more precise.
In addition, after a hole has been made by a punch tool, it is possible to use the camera to measure and store any error within allowed tolerances between the actual position of the hole made and the corresponding mark on the printed circuit panel. By calculating the mean error for all of the holes made in succession by the same tool, it is possible on the basis of said mean value to correct the displacement instructions that are transmitted by the central calculator of the machine to the punch block.
This operation which is itself made possible by having precise control over the positioning of each punch block in the X and Y directions and in rotation, makes it possible in turn to escape from the cumulative effect of manufacturing tolerances concerning the various parts of the punch tools.